Wow! I'm impressed.Just to chime in, in my ercexienpe "volunteers" are students (if the research is conducted in an academic setting or on a campus) or people culled from the general population via ads in newspapers, etc. I see these all the time in our daily paper here. I've heard that some people "volunteer" for medical research for a living, but can't really back that up with any facts that I know of. I can't help but wonder what confounding variables these kinds of "volunteers" bring to a study.Also, the subject populations are often small. Many studies you'll see quoted all the time in general media are based on, for example, 12 Harvard undergraduates, who were required to volunteer for the subject "pool" if they majored in any social science.